1. Field of the Invention
The present invention pertains to copolymers useful for photoimaging compositions. These copolymers are comprised of a fluoroalcohol or protected fluoroalcohol functional group and a repeat unit derived from an acrylate monomer containing a fluoroalkyl group or a hydroxyl substituted alkyl group. Such groups have been found to promote adhesion of the copolymers, and photoresists derived from such copolymers, to substrates used in the manufacture of semiconductor devices. The copolymers are especially useful in photoresist compositions having high UV transparency (particularly at short wavelengths, e.g., 193 nm and 157 nm).
2. Description of Related Art
Polymer products are used as components of imaging and photosensitive systems and particularly in photoimaging systems. In such systems, ultraviolet (UV) light or other electromagnetic radiation impinges on a material containing a photoactive component to induce a physical or chemical change in that material. A useful or latent image is thereby produced which can be processed into a useful image for semiconductor device fabrication.
For imaging features at the submicron level in semiconductor devices, electromagnetic radiation in the far or extreme ultraviolet (UV) is needed. Photolithography using 193 nm exposure is a leading candidate for future microelectronics fabrication using 0.18 and 0.13 μm design rules; photolithography using 157 nm exposure may be needed for 0.100 μm or less design rules. The opacity of traditional near-UV and far-UV organic photoresists at 193 nm or shorter wavelengths precludes their use in single-layer schemes at 157 nm.
Photoresists comprising copolymers with fluoroalcohol functional groups have been disclosed in WO 00/67072.
Copolymers of fluorinated alcohol monomers with other comonomers have been reported (U.S. Pat. No. 3,444,148 and JP 62186907 A2). These patents are directed to membrane or other non-photosensitive films or fibers, and do not teach the use of fluorinated alcohol comonomers in photosensitive layers (e.g., resists).
There is a critical need for other novel resist compositions that have high transparency at 193 nm, and more preferably at or below 157 nm, and also have other key properties such as good plasma etch resistance and adhesive properties.